There's a reason behind it. When you installed any new programs with automatic configurations, these kind of stuffs happens
Go to control panel, click uninstall a program, and here you will see some programs names with 'search toolbar'.
double click (uninstall it). it will be uninstalled! you can go back to chrome and click new tab and it will go back to the normal stuff
and remove unknown extensions from Chrome
andgoto --> settings --> on startup ---> open the new Tap page (or) Open a specific page or set of pages (there u can set what page will open whenever u open the chrome browser)